Reddit reviews The Classics 12-Pack Soft Foam Pencil Grips, Assorted Colors, 1.5-Inch Long (TPG-16412)

Sure can.

https://www.amazon.com/Classics-Pencil-Assorted-1-5-Inch-TPG-16412/dp/B00GN1YN8U/ref=sr_1_5?s=office-products&ie=UTF8&qid=1522764007&sr=1-5&keywords=pencil+grips

My son uses them to help with his handwriting as he has poor motor skills due to autism.

Thank you, I’ve learnt a bit through trial and error since I was diagnosed. Unfortunately I’m not a knitter (or at least a very poor one),this is all I’ve found.

https://www.verywellhealth.com/list-of-adaptive-aids-for-knitting-and-crocheting-1094601
https://www.amazon.com/Classics-Pencil-Assorted-1-5-Inch-TPG-16412/dp/B00GN1YN8U/ref=sr_1_9?s=office-products&ie=UTF8&qid=1542481296&sr=1-9&keywords=Pencil+grips I truly don’t know if these would work on a knitting needle or not.

Unfortunately I can’t find much on knitting with arthritis. Perhaps it would be worthwhile posting to the r/rheumatoid subreddit, they are very helpful there. And r/knitting has a lot of subscribers as well so hopefully you will get some good ideas there as well.

Sorry I’m not much help. It’s not often you find more on crochet than knitting!

Have you considered getting a pen grip made from a gel or cushion-y material for your Staedtler Fineliners, as you seem to like those the best but they hurt your fingers? I've seen tons of options at office supply stores -- something like this, perhaps?

https://www.amazon.com/Classics-Pencil-Assorted-1-5-Inch-TPG-16412/dp/B00GN1YN8U/

or

https://www.officedepot.com/a/products/595233/Office-Depot-Brand-Gel-Pencil-Pillows/

these?

This is a bit of a kludge, but if you like the way the pen writes and want to have a bit more comfortable grip, it is a perfect size to slip on the little 'foam tubes' that are made to improve the comfort of a pencil grip. (Like these) You can just slip it on from the back end of the barrel (so you don't go over the inky nib) and right up over the gripping area, and then slip it off when you are done using the pen. When I wanted to write a couple of letters or something, this made it more comfortable.

This pen, and an identical model in a gun-metal blue, were the first two pens I purchased when I got interested in FPs about seven years ago. Purchased from Ron Zorn at Main Street Pens, whom I've remained friends with since then.

Judging by the size and shape in pictures, I think you could just get those rubber grips for pencils. https://smile.amazon.com/dp/B00GN1YN8U/

I use pencil grips. They slide on easily and stay on pretty well. I haven’t had a frayed cord since I started using them. Plus they are kind of cute. Similar to these: https://www.amazon.com/Classics-Pencil-Assorted-1-5-Inch-TPG-16412/dp/B00GN1YN8U